文档介绍：Chapter 5 Macromolecules and Molecular ics
The key informational macromolecules in prokaryotic and eukaryotic cells are DNA, RNA, and protein.
Molecular ics deals with the mechanisms by which the information in DNA is replicated, and by which it can be transcribed into RNA and translated into specific proteins.
Central Dogma of Molecular Biology 中心法则
One-way transfer
of ic information
from nucleic acid
to protein is call
Central Dogma of
Molecular Biology
Information Transfer in Prokaryotes and Eukaryotes
Prokaryotes
Eukaryotes
DNA Synthesis proceeds 5’ 3’
A: Adenine
G: Guanine
T: Thymine
C: Cytosine
Replication of DNA proceeds by insertion of a new nucleoside triphosphate at the free 3’-hydroxyl end, with loss of two phosphate
DNA double helix
Many important proteins interact with the major groove of DNA double helix
How DNA is supercoilded and relaxed
Enzyme involved in supercoiling (in bacteria):
DNA gyrase (旋转酶):
DNA Topoisomerase II (DNA拓朴异构酶II)
Enzyme involved in removing supercoiling:
DNA gyrase:
DNA Topoisomerase I
Two antibiotics (Nalidixic acid and Novobiocin) inhibit the action of DNA.
Secondary Structure of DNA
DNA bending: involving several runs of five to six adenines (in the same strand), each separated by four or five bases;
Inverted repeat: regions of DNA containing repeated sequences in inverse orientation, leading to a stem-loop (茎—环);
Sticky end: DNA with single-plementary sequences at the end, this can form a hairpin, linear DNA can form a cycle with their sticky end.
These structures influence DNA interaction with proteins
The effect of temperature on DNA structure
Two hydrogen bonds hold adenine-thymine (A-T) together;
Three hydrogen bonds hold guanine-cytosine (G-C) together;
Thus, G-C pairs are stronger than A-T pairs;
The separation of double stranded DNA by heating is called melting;
DNA with higher GC content has higher melting temperature;
Organisms living at high T has higher GC content.